Before you begin, does Mountain Lion support your Mac? Mountain Lion does not support Macs older than 2007 - 2009.

If it does, and you have at least 2GB of memory, then go to App Store (the App Store should be on your Mac if you have OS 10.6.8). Purchase and download Mountain Lion and install. The current version of Mountain Lion is OS 10.8.4.

Note: OS 10.6.8 is the last version of Snow Leopard released, therefore you have the "newest version" of Snow Leopard.

I'm currently running Mac OS X 10.5.8 on my MacBook. I'm actually trying to install the World of Warcraft but I can't cause my macbook version is too old. I need 10.7.3 or newer. Which version should I upgrade to to play this game? Am I supposed to buy 10.6 snow leopard then upgrade to maverick or some other version to play this game? I don't have a mac app store I can't download maverick.

If your iMac has 10.5.8, then you have Mac OS X Leopard. The .8 in 10.5.8 means there have been 8 updates applied to the base 10.5.0 version. Mac OS X Snow Leopard is version 10.6 which you do not currently own, but can be purchased for $29 from any Apple Store.

As far as your question of benefits to upgrading, yes there are some new features and fixes in Mac OS X Snow Leopard† that many will find beneficial. You do need to be sure your iMac meets the system requirements, which mainly is that it contains an Intel processor.

For your final question on Word, you have some options. Microsoft has released Microsoft Office for OS X, which can be purchased in an Apple Store. Also you can use OS X's Boot Camp feature if you would like to run Word natively in Windows. Finally, you can look into virtualization software. Some examples of these are VMWare Fusion, and Parallels.

Your MacBook Pro model will determine which OS you can go to.
(From OS 10.6.8 you can go directly to OS 10.7, OS 10.8, or OS 10.9 but that depends on your hardware.)

Go to "About This Mac" under the "Apple" menu. Select "More Info" and then select "System Report". In "Hardware Overview" make note of the Model Identifier.

If the Model Identifier is MacBookPro1,1 or MacBookPro1,2 the maximum OS that can be installed is OS 10.6 (which you have).
If the Model Identifier is MacBookPro2,1 or MacBookPro2,2 the maximum OS is OS 10.7.
If the Model Identifier is MacBookPro3,1 or later the current maximum OS is OS 10.9.

(You probably have a MacBookPro3,1 or MacBookPro4,1 model since you have a 2.4ghz processor.)

All OS versions after OS 10.6 are installed through the App Store app (which you have on your Mac with OS 10.6.8). OS 10.9 is free and easy to find in the App Store app by typing "OS X Mavericks" in the search box at the top right of the App Store app window. To get OS 10.7 or OS 10.8 you need to first purchase a redemption code from the online Apple Store which will give you access to these OS versions in the App Store app.

Links to purchase redemption code for OS 10.7 and OS 10.8 can be found on these pages:
Canada: storeDOTappleDOTcom/ca/help/downloadable_software#MacOSX (replace "DOT" with ".")
USA: storeDOTappleDOTcom/us/help/downloadable_software#MacOSX

To determine the type of processor, go to "About this Mac" in the "Apple" menu. If the word "Intel" appears anywhere next to "Processor", you can install Snow Leopard. You need at least 1GB of memory, 2GB or more is better.

TIP: Consider installing Snow Leopard on a separate partition (especially since Snow Leopard may need to do some reformatting of the partition it is being installed to). With an OS installed on two partitions, you can then start up from either the Tiger partition or the Snow Leopard partition by pressing the Option Key during startup (or using the Start Up Disk preference in System Preferences). This lets you keep you OS 10.4.11 installation in case you want to jump back.

BTW: If installing to a new partition, Snow Leopard installer will search your Mac for other OS installations and ask you if you want to import OS settings, apps, and/or files from an older installation. Say yes to all for a smoother transition to Snow Leopard. All settings, compatible apps/drivers and files will be copied to the new partition.

If you could upgrade the hardware such as ram, that would be a good idea before upgrading to a new version of OS X. Otherwise, I highly recommending NOT upgrading because it will cause extreme bottleneck and performance to slow down.

It is always wise to have protection. Even with Mac's being a low target of viruses. Typically you can pick up a computer virus although, it might not affect your Mac you can pass it on to your Windows Friends/Co-workers. Rather you use Snow Leopard or any other version of Mac OS you should consider an antivirus software. However, I would not rush out in panic.

I need to set up a new ProPresenter v5 workstation. Our current station has been running flawlessly on a 2013 iMac with 10.7.5, so I don't want to gamble on Yosemite so early, and I'm not geeky enough to feel confident installing a downgrade myself.

Snow Leopard requires a Mac with an Intel-based processor (not a PowerPC processor) and at least 1GB of memory.

You're good on the memory. Most likely you are good on the processor.

(OS 10.5.8 was the last OS to support the PowerPC processor. The processor can not be changed. To find out which processor you have go to Apple Menu --> About This Mac and see if the word "Intel" or "PowerPC" is in the description next to "Processor".)

Apple transitioned from PowerPC processors to Intel processors about 2006.

i recently bought an Intel imac late 2006 1.83ghz running 10.5 and i wanted to upgrade it to 10.6 but i don't have any of the original disks or any of the previous owners information. so i want to know if i need anything like the originals owners information or any of the disks that came with it.

What is the Model ID of your MacBook? The model ID can be found by going to Apple Menu --> About This Mac --> More Info . . . > System Report --> Hardware Overview --> Model Identifier.

Since your MacBook has a 2.4GHz Intel Core 2 Duo processor it likely has an ID of Macbook5,1 (late 2008) or Macbook7,1 (mid 2010). Since it has OS 10.5.8, it is probably Macbook5,1.

Either model can be upgraded to OS 10.6 Snow Leopard.

Once OS 10.6 is software updated to OS 10.6.8, and with a minimum of 2GB memory (or arbeitsspeicher), the MacBook can be upgraded directly to the latest OS: OS 10.10 Yosemite.

For performance, you may wish to also consider increasing the MacBook's memory to 4GB. (4GB is maximum memory that is officially supported on MacBook5,1 or Macbook7,1. Note that up to 8GB can be put in Macbook5,1 and up to 16GB can be put in Macbook7,1, but only 4GB is "officially" supported by either model.)